Recessed Contact Structures and Methods
An exemplary method of forming a semiconductor device includes forming, in a substrate, an active region protruding vertically from a major surface of the substrate, the active region including a semiconductor source-drain (S/D) region and a first 3-D channel structure, the S/D region physically contacting the first 3-D channel structure, and forming an opening extending into the S/D region, the opening having a depth greater than half of a height of the first 3-D channel structure; and forming a metallic plug in the opening, the metallic plug making electrical contact with the S/D region.
This application claims the benefit of U.S. Provisional Application No. 63/138,120, filed on Jan. 15, 2021, and U.S. Provisional Application No. 63/234,987 filed on Aug. 19, 2021, which application is hereby incorporated herein by reference.
TECHNICAL FIELDThe present invention relates generally to a structure and method for fabricating semiconductor devices, and, in particular embodiments, to a recessed contact structures and methods for fabricating semiconductor devices.
BACKGROUNDA semiconductor device such as an integrated circuit (IC) is a monolithic structure comprising an integrated network of electronic components and multiple levels of interconnect. Generally, the device is fabricated by sequentially depositing and patterning dielectric, metal, and semiconductor layers over a semiconductor substrate to form circuit components such as transistors, resistors, and capacitors, and connectors such as contacts, metal lines, and vias. At each new technology node, the feature sizes are shrunk, roughly doubling the packing density to reduce cost and increase functionality of IC's. Enabled by innovations such as self-aligned double and quadruple patterning (SADP and SAQP), extreme ultraviolet (EUV) lithography, atomic level deposition and etch (ALD and ALE), area selective deposition (ASD), and self-aligned processes (e.g., self-assembled monolayers (SAM)), the patterns in advanced IC's have features down to about ten nanometers. But, miniaturization also increases electric fields in a field-effect transistor (FET). Hence, the supply voltage is periodically reduced to meet transistor reliability and leakage constraints, which adversely affects the drive capability per unit area.
A three-dimensional (3-D) channel structure, for example, a fin-shaped FinFET or a vertical stack of nanosheets of a gate all-around (GAA) FET is used to recover the drive current. Typically, the source-drain (S/D) of a 3-D FET are raised semiconductor regions formed along two opposite sides of the 3-D channel structure, with the S/D contacts made to a top surface of the S/D. In such architecture, the transistor current has to flow vertically through the raised S/D to access the 3-D channel structure. For a transistor array drawn at a minimum pitch, this vertical flow must squeeze through a narrow cross-section because the space for S/D contacts between adjacent gates is barely a few nanometers in an advanced IC design. Constricting the S/D cross-section in the path of the current causes a sharp increase in series resistance that may limit the drive current of a 3-D FET. Incorporating a wrap-around contact (WAC) provides partial relief by forming a metal liner wrapping around the bottom and sides of the S/D, but at the cost of an expensive and complex process flow. Novel contact structures and methods to further reduce parasitic series resistance of a 3-D FET may be beneficial for continued scaling.
SUMMARYA method of forming a semiconductor device, the method includes: forming, in a substrate, an active region protruding vertically from a major surface of the substrate, the active region including a semiconductor source-drain (S/D) region and a first 3-D channel structure, the S/D region physically contacting the first 3-D channel structure, and forming an opening extending into the S/D region, the opening having a depth greater than half of a height of the first 3-D channel structure; and forming a metallic plug in the opening, the metallic plug making electrical contact with the S/D region.
A method of forming a semiconductor device, the method includes: forming a plurality of nanosheets including a first nanosheet and a second nanosheet, each of the plurality of nanosheets having a horizontal central plane and spaced apart from one another in a vertical direction; forming a source-drain (S/D) region at a distal end of each of the plurality of nanosheets; from a major surface of the S/D region, forming an opening extending through the horizontal central planes of the first and the second nanosheets into the S/D region; and filling the opening with a metal to make electrical contact with the first and the second nanosheets through the S/D region.
A semiconductor device includes: an active region protruding vertically from a major surface of a substrate, the active region including a semiconductor source-drain (S/D) region and a first 3-D channel structure, the S/D region physically contacting the first 3-D channel structure, and an opening extending into the S/D region, a bottom of the opening being below the first 3-D channel structure; and a metallic plug disposed in the opening, the metallic plug being electrically coupled to the S/D region.
For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
This disclosure describes embodiments of a method of fabricating 3-D field-effect transistors (FET's) in which contacts to a source/drain (S/D) region are made using a novel recessed contact architecture where a contact metallization feature is formed in the semiconductor material of the S/D of an FET. Use of the embodiments described in this disclosure provides the advantage of achieving densely packed 3-D FET's without a high penalty in increased parasitic S/D resistance in series with the 3-D channel structure. Example fabrication methods for forming the novel contact structures with a self-aligned contact (SAC) process flow are provided. As described in further detail below, the fabrication methods utilize a relatively low-cost and low-complexity sequence of process steps that have demonstrated manufacturability.
As explained above in the background section, the transistor current in 3-D FET's (used in several advanced complementary metal oxide semiconductor (CMOS) technologies) flows vertically through raised S/D regions that are barely a few nanometers wide. The conductivity of even a heavily doped and strained semiconductor (e.g., carbon-doped silicon and embedded silicon-germanium) is low relative to that of most metals. Thus, for conventional contact architecture, where the contact metallization terminates on a top surface of the S/D, the parasitic S/D resistance in series with the transistor channel is very high. Even in WAC architecture, where much complex processing is performed to add a metal liner around the periphery of the S/D region, the S/D resistance persists being undesirably high. An IR voltage drop in the extrinsic S/D resistance subtracts from the power supply voltage (VCC) in driving the intrinsic device. With VCC scaled down to about 1 V, S/D resistance may very well be the limiting constraint for the current-drive capacity of the device. The voltage loss gets worse for the portions of the 3-D channel structure that are further from the metal contact.
Embodiments of a novel contact architecture are described in this disclosure that provide a low resistance path in close proximity to the entire channel structure along the vertical dimension of the S/D. The low resistance path is a recessed metal feature in the S/D, formed by extending a contact opening from a top surface of the S/D region to a depth substantially close to the deepest portion of the channel structure and subsequently filling the opening with metal. This metallic extension of the conventional S/D contact structure may be fabricated using, for example, a conventional SAC flow with relatively minor modifications, as described in further detail below. The recessed S/D contact architecture provides low-cost methods that not only improve the total drive current but also results in distributing the current more evenly along the height dimension of a 3-D channel structure.
The recessed S/D contact structure and method is presented in the context of the GAAFET, which is likely be the transistor structure of choice for sub-5 nm CMOS nodes and is expected to benefit by using the embodiments described in this disclosure.
The GAAFET has a 3-D channel structure comprising a vertically arranged stack of, generally, three to five tiers of discrete nanosheets through which the channel current flows horizontally between distally located S/D regions at two opposing ends. Each nanosheet is a sheet of semiconductor having a horizontal central plane and a thickness or height dimension, H, that is typically about 3 nm to 10 nm in the direction normal to the central plane. Of the two nanosheet dimensions in the central plane, a length dimension, L, refers to a distance separating the distal S/D regions in a direction parallel to the channel current and a width dimension, W, refers to a lateral dimension perpendicular to the length direction. A transistor's gate region is generally a multi-layered stack including a high dielectric constant (high-k) gate dielectric and a metal gate electrode, usually referred to as an HKMG gate. The HKMG gate of the GAAFET wraps around each nanosheet and connects to columnar HKMG regions along the two opposing sides of the nanosheet that are orthogonal to the sides having the S/D regions.
In a fabrication process flow of a semiconductor device, the transistor structure is formed from a starting semiconductor substrate using a sequence of process steps, generally referred to as the front-end-of-line (FEOL). In this disclosure, a description of an example FEOL that may be used in constructing a GAAFET is provided with reference to
A sequence of process steps used in forming the contacts is usually referred to as the middle-of-line (MOL). In this disclosure, various example embodiments of structures and methods for forming a recessed S/D contact to S/D regions of GAAFET's are described with reference to
The recessed S/D contact methodology has been concisely stated in a flow diagram illustrated in
In the example embodiments described in this disclosure, the sacrificial nanosheets 151, 153, 155, and 157 may be silicon-germanium nanosheets and the channel nanosheets 152, 154, and 156 may be silicon nanosheets.
The isolation regions 120 comprise insulating regions disposed along opposing sides of the active regions 110 separating adjacent active regions 110. The semiconductor region below a major surface of the isolation region is referred to as the semiconductor substrate 130. For example, the semiconductor region below the heterostructure 150 and the semiconductor region below a top portion of the fin 140 have been included in semiconductor substrate 130 for simplicity.
The active regions 110 and the isolation regions 120 may be formed using a shallow trench isolation (STI) method. In the STI method, first the starting semiconductor substrate is patterned to recess the semiconductor surface to a desired depth, as mentioned above. In some embodiments, an anisotropic etching process such as reactive ion etching (RIE) may be performed with a patterned hard mask formed using, for example, a self-aligned double patterning (SADP) method, as mentioned above. For the FinFET structure 100-1, the recess extends beyond the bottom of an active channel region, indicated in
The 3-D channel structure of the FinFET structure 100-1 (illustrated in
It is noted that in a FinFET structure, such as the FinFET structure 100-1, the bottom of the active channel region is at a level coplanar with a major surface the isolation region 120. Hence, a height dimension, HFIN, of the channel region of the FinFET structure 100-1 is a vertical distance between the top of fin 140 and the level of the major surface of the isolation region 120, as illustrated in
The rest of this disclosure describes several example embodiments of the recessed S/D contact in the context of the GAAFET only. However, it is understood that the recessed S/D contact may be implemented for FinFET's and GAAFET's using similar processes and structures.
In some embodiments, the GAAFET is fabricated using a replacement metal gate (RMG) method. In the RMG method, first a sacrificial gate structure is fabricated after forming the isolation regions 120. A sidewall structure is formed around the sacrificial gate structure, and the combined sacrificial gate and sidewall structures are used to define self-aligned channel, S/D, and gate regions of the GAAFET.
As illustrated in the planar view (X-Y plane) in
Typically, the features of the sacrificial gate pattern are shaped like lines that are orthogonal to the active region 110, as illustrated in the planar view in
Removing the heterostructure 150 self-aligned to the sidewall structures 220, defines a self-aligned channel region comprising the channel nanosheets 152, 154, and 156 in the remaining portions of the heterostructure 150. The horizontal central planes, HP1, HP2, and HP3, illustrated in
In this disclosure, we refer to an area as a disjoint S/D active section if the area is an active region and if there is no gate structure formed over that section of the active region. For example, as illustrated in
As explained in further detail below, the semiconductor material of the S/D regions may be deposited in the disjoint S/D active sections by epitaxial growth from exposed surfaces of the channel nanosheets 152, 154, and 156, exposed along sidewalls of the recess 240 in the vertical X-Z plane. The S/D region originating from a disjoint S/D active section may merge with adjacent S/D regions to form an elongated S/D region extending over several adjacent disjoint S/D active sections in the width direction (X-direction in
As understood from the cross-sectional view of the Y-Z plane illustrated in
In some embodiments, an optional insulating region may be formed over a portion of a major surface of the substrate 130, the optional insulating region being referred to as an insulating cover layer 250. In some embodiments, the insulating cover layer 250 may be formed over the bottom of the recess 240 to insulate the substrate 130 exposed by removing the heterostructure 150 between adjacent sidewall structures 220. In some other embodiments, the surface of the semiconductor substrate 130 at the bottom of the recess 240 may not be insulated from the subsequently formed S/D layers. In the example embodiment illustrated in
It is noted (see
In addition, in
In addition to covering the disjoint S/D active region with the semiconductor S/D layer 310, the epitaxially grown S/D region covers a portion of the isolation region 120 adjacent to the disjoint S/D active region no. As seen in
In some designs, active regions, such as the active region no (see
The epitaxially grown S/D layer 310 is generally a heavily doped semiconductor layer. For an n-type FET, the S/D layer 310 may be phosphorus or arsenic doped silicon or silicon-carbon alloy to form a strained S/D layer 310 that may induce tensile strain in the channel nanosheets 152, 154, and 156 to enhance electron mobility. For a p-type FET, the S/D layer 310 may be boron doped silicon or silicon-germanium alloy to form a strained S/D layer 310 that may induce compressive strain in the channel nanosheets 152, 154, and 156 to enhance the mobility of holes.
In some embodiment, the CESL 320 may comprise silicon nitride and the contact ILD 330 may comprise silicon oxide or a low-k silicon oxide (e.g., CDO, fluorosilicate glass (FSG), a porous oxide, or the like). In various other embodiments, the CESL may comprise silicon carbide, aluminum oxide, or titanium dioxide. The contact ILD 330 is part of an interlayer dielectric through which a contact to the S/D region would be made subsequently, as described in further detail below. The deposited dielectric layers CESL 320 and contact ILD 330 may be etched back and planarized using a CMP process.
A S/D anneal step, for example, a rapid thermal anneal (RTA), may be performed to repair crystal defects, activate the dopants in the S/D layer 310, and diffuse some of the dopants into the channel nanosheets 152, 154, and 156 in the regions covered by the sidewall structure 220 and the inner spacers 222. The S/D anneal step helps reduce the parasitic S/D resistance in series with the 3-D channel structure.
As mentioned above, the GAAFET structure 300 illustrated in
In the RMG method, the sacrificial gate stack comprising the sacrificial gate dielectric layer 214 and the sacrificial gate electrode layer 210 is removed and replaced with an HKMG gate. In some embodiment, the sacrificial gate stack may be removed in two steps. First, the sacrificial gate electrode layer 210 is removed selective to the sacrificial gate dielectric layer 214 and, subsequently, the sacrificial gate dielectric layer 214 is removed selective to the nanosheet heterostructure 150. The etch processes may be performed using suitable known etch chemistries and etching techniques. For example, in some embodiment, ammonium hydroxide or tetramethylammonium hydroxide (TMAH) wet etching or sulfur hexafluoride plasma dry etching may be used for removing amorphous silicon and, hydrofluoric acid (HF) wet etching or dry etching with HF vapor may be used for removing silicon oxide.
As mentioned above, each of the channel nanosheets 152, 154, and 156 in
The recesses formed by removing the sacrificial layers are filled with the HKMG gate. The high-k gate dielectric layer 420 is formed in adjacent to the channel nanosheets 152, 154, and 156 and the metal gate electrode layer 410 is formed over the high-k gate dielectric layer 420. The metal gate electrode layer 410 comprises a combination of several layers, including a workfunction metal layer formed in close proximity to the high-k gate dielectric layer 420. In some embodiments, the various layers for the HKMG gate may be formed using a highly conformal process such as ALD. A workfunction metal layer may also comprise several metal layers and may include metals such as titanium nitride, tantalum nitride, and metal alloys such as AlC, TiAl and TiAlC. The workfunction metal for an n-type FET is generally different from that for a p-type FET in order to select different threshold voltages for the different types of FET. Metal deposition is continued till the recesses are filled with excess metallic fill material. In some embodiments, the metallic fill material may be different from the workfunction materials and may comprise a low resistivity metal, for example, tungsten, copper, cobalt, and aluminum. In some embodiments, the space between vertically adjacent channel nanosheets may be pinched off by the workfunction metal layer prior to depositing the metallic fill material.
After depositing the metallic fill, excess metal is removed by a planarizing etchback process (e.g., a metal CMP process) down to the previously planarized level of the contact ILD 330 and the sidewall structures 220 (see
After planarization, a selective recess etch is used to recess the conductive portion of the surface, a capping dielectric (e.g., silicon nitride) is deposited conformally, and the capping dielectric is etched back using a planarization process to form a self-aligned contact (SAC) cap 430 inlaid between sidewall structures 220 over the tops of the gate electrode layer 410. The structure formed after the SAC cap CMP is the GAAFET structure 400, shown in cross-sectional view of the Y-Z plane illustrated
As illustrated in
The channel region of the GAAFET structure 400 in
Next, the formation of various embodiments of the recessed S/D contact using the GAAFET structure 400 (illustrated in
In the GAAFET structure 500 illustrated by
As described above with reference to
One advantage provided by the spacer 610 is that it better ensures that the lateral dimensions of the exposed surface of the S/D layer 310 are precisely controlled. As explained in further detail below, a controlled lateral spacing between the position of the opening and the nanosheets 152, 154, and 156 helps a leakage component of a GAAFET. Once the S/D layer 310 is exposed, a third etch process that removes a portion of the S/D layer 310 may be performed, as mentioned above and described in detail below.
In some embodiments, the semiconductor S/D layer 310 may comprise heavily doped n-type silicon or a silicon-carbon alloy for the n-type GAAFET's and heavily doped p-type silicon or a silicon-germanium alloy for the p-type GAAFET's. In some embodiments, the third etch may be simultaneously removing portions of the S/D layers 310 of the n-type GAAFET and the p-type GAAFET. In some other embodiments, additional masking steps may be inserted in the fabrication process flow to allow for the use of separate the etch processes for n-type and the p-type GAAFET's. This simplifies the process design for the third etch but at a higher processing cost. In the example embodiments in this disclosure, both types of GAAFET's are etched at the same time with an anisotropic RIE process using, for example, chlorine based or hydrogen bromide based etch chemistry along with an oxygen source (e.g., oxygen, carbon monoxide, or carbon dioxide) for passivating the sidewalls and an inert gas (e.g., argon or helium) for dilution.
In this embodiment, the third etch may be an endpoint etch using the insulating cover layer 250 as the etch stop layer. In some other embodiment, a timed third etch may be used, even if the cover layer 250 present. In some embodiments, where the optional cover layer 250 is not present, the third etch may be a timed etch, where the etch time is selected to prevent recessing the substrate 130. Generally, it is desirable to select an etch time for the timed etch processes such that the bottom of the recessed contact opening is positioned in a horizontal plane that is in the semiconductor S/D layer 310 but deeper than the top of the channel nanosheet 152 (the nanosheet closest to the substrate 130). In all embodiments, the recessed contact is formed to place the bottom of the contact at a depth greater than half the height, HCH, of the 3-D channel structure.
As mentioned above, one advantage of forming the spacer 610 is that the lateral dimension of the contact opening 520 (see
The metal plugs 810 and 815 are formed by first depositing a conductive layer that overfills the recessed contact openings 720 and 750 (or the lowest level of a top surface of the conductive layer exceeds the highest level of a planarized surface of the interlayer dielectric comprising the contact ILD 330). The deposition process may include forming a conductive liner prior to completing filling the recessed contact openings 720 and 750. The conductive liner may be formed lining the sides and the bottom of the recessed contact openings 720 and 750, where the conductive liner includes a metal that can chemically react with the semiconductor to form a conductive metal silicide during a subsequent thermal process step. Examples of metals that can react with silicon, silicon-carbon alloy, and silicon-germanium alloy to form a metal silicide include titanium, cobalt, nickel, platinum, and ruthenium. In various embodiments, other metals used as a conductive liner include tantalum, titanium nitride, tantalum nitride, or a combination thereof. Metals used to fill the recessed contact openings 720 and 750 comprise tungsten, copper, cobalt, ruthenium, and the like.
After the contact metal deposition to form a conductive layer overfilling the recessed contact openings 720 and 750 is complete, a planarization process (e.g., a metal CMP process) is performed to remove excess conductive material from over the interlayer dielectric comprising the contact ILD 330 to form a substantially planar top surface comprising an insulating portion and a conductive portion, the conductive portion being the top surface of the metal plugs 810 and 815 in the openings 720 and 750, respectively, as illustrated in
In some embodiments, where the processing flow includes a thermal step to form a metal silicide, as mentioned above, the silicidation process steps may be performed after the contact metals have been deposited and prior to the planarization step to form the metal plugs 810 and 815 inlaid in the contact openings 720 and 725, respectively. In some other embodiments, the silicidation process steps may be performed after the conductive liner has been formed and before all the metal deposition steps to form the conductive layer filling the contact openings 720 and 725 have been completed.
As indicated in block 910, the method comprises forming in a substrate an active region, e.g., having four lateral sides, protruding vertically from the substrate. For example, as discussed with reference to
In block 920, a recessed contact opening is formed (e.g., the recessed contact openings 720 and 725, as discussed with reference to
As indicated in block 930, the recessed contact opening formed in block 920 is filled by a metal plug inlaid in the recessed contact opening (e.g., the metal plugs 810 and 815, as discussed with reference to
As indicated in block 950 in
As indicated in block 960 in
In block 970 of the block diagram for the method 940 an opening is formed extending from a major surface of the S/D region into the S/D region (e.g., the openings 720 and 725, as discussed with reference to
As indicated in block 980, the method 940 includes filling the opening with a metal to make electrical contact with the first and the second nanosheets through the S/D region. For example, the metallic features 810 and 815 make electrical contact with the first and the second nanosheets 156 and 154 through the S/D region 310, as discussed with reference to
The embodiments of the recessed S/D contacts described above provide contact structures and methods that provide low S/D series resistance in 3-D FET's such as FinFET's and GAAFET's. By using these embodiments, densely packed 3-D FET's may be achieved without a high penalty in increased parasitic S/D resistance in series with the 3-D channel structures. The recessed contact includes a vertical metallic feature embedded in the semiconductor S/D, which helps distribute the transistor current more evenly vertically across the fin of a FinFET and among the channel nanosheets of the multi-tiered 3-D channel structure of the GAAFET.
In addition, the inventors infer from the geometry of the combined 3-D FET and recessed S/D contact structure and from known properties of deposited films (e.g., the coefficient of thermal expansion) that, in various embodiments, the materials and dimensions of the recessed contact may be engineered to adjust the strain in the epitaxially-grown S/D region to enhance channel mobility of some of the GAAFET's. Yet another benefit of the recessed contact is that, by reducing the S/D resistance, the recessed contact reduces non-ideality of the transistor I-V, thus rendering higher accuracy of compact models of the FET. Compact models of FET's are computer simulation models used in computer-aided design (CAD) tools for designing IC's. Standard compact models may not accurately reproduce non-idealities in transistor I-V characteristics introduced by high S/D resistance, particularly, nonuniform or distributed S/D resistance.
Example 1. A method of forming a semiconductor device, the method includes: forming, in a substrate, an active region protruding vertically from a major surface of the substrate, the active region including a semiconductor source-drain (S/D) region and a first 3-D channel structure, the S/D region physically contacting the first 3-D channel structure, and forming an opening extending into the S/D region, the opening having a depth greater than half of a height of the first 3-D channel structure; and forming a metallic plug in the opening, the metallic plug making electrical contact with the S/D region.
Example 2. The method of example 1, where forming the active region includes forming a first sacrificial gate stack over the first 3-D channel structure, where forming the metallic plug includes forming a portion of the metallic plug along a sidewall of the first sacrificial gate stack.
Example 3. The method of one of examples 1 or 2, where the active region includes a second 3-D channel structure, the S/D region physically contacting the second 3-D channel structure.
Example 4. The method of one of examples 1 to 3, further including: forming a first sacrificial gate stack over the first 3-D channel structure and a second sacrificial gate stack over the second 3-D channel structure, where forming the metallic plug includes forming a portion of the metallic plug along a sidewall of the first sacrificial gate stack and a sidewall of the second sacrificial gate stack.
Example 5. The method of one of examples 1 to 4, where forming the active region includes forming an insulating region over a portion of the major surface of the substrate.
Example 6. The method of one of examples 1 to 5, where forming the opening exposes a surface of the insulating region.
Example 7. The method of one of examples 1 to 6, where the S/D region is covered by an insulating contact interlayer dielectric (ILD), and where forming the opening includes: performing a first etch process to form a first opening in the contact ILD, the first opening exposing a contact etch stop layer covering a surface of the S/D region; after completing the first etch process, forming a spacer over sidewalls of the first opening; performing a second etch process to remove the exposed contact etch stop layer; and performing a third etch process to extend the first opening into the S/D region.
Example 8. The method of one of examples 1 to 7, where the spacer includes silicon oxide, or silicon nitride.
Example 9. The method of one of examples 1 to 8, further including: after completing the third etch process, selectively removing the spacer formed in the first opening.
Example 10. The method of one of examples 1 to 9, further including: siliciding a portion of the S/D region exposed by the opening.
Example 11. The method of one of examples 1 to 10, where the siliciding forms a metal silicide including titanium silicide, cobalt silicide, nickel silicide, platinum silicide, or ruthenium silicide.
Example 12. A method of forming a semiconductor device, the method includes: forming a plurality of nanosheets including a first nanosheet and a second nanosheet, each of the plurality of nanosheets having a horizontal central plane and spaced apart from one another in a vertical direction; forming a source-drain (S/D) region at a distal end of each of the plurality of nanosheets; from a major surface of the S/D region, forming an opening extending through the horizontal central planes of the first and the second nanosheets into the S/D region; and filling the opening with a metal to make electrical contact with the first and the second nanosheets through the S/D region.
Example 13. The method of example 12, where filling the opening with a metal includes filling with tungsten, copper, cobalt, ruthenium, titanium, tantalum, titanium nitride, tantalum nitride, or a combination thereof.
Example 14. The method of one of examples 12 or 13, where filling the opening with a metal includes forming a conductive liner along sides and a bottom of the opening prior to filling the opening with the metal.
Example 15. The method of one of examples 12 to 14, where the conductive liner includes titanium, titanium silicide, cobalt, cobalt silicide, nickel, nickel silicide, platinum, platinum silicide, ruthenium, ruthenium silicide, titanium nitride, tantalum, tantalum nitride or a combination thereof.
Example 16. A semiconductor device includes: an active region protruding vertically from a major surface of a substrate, the active region including a semiconductor source-drain (S/D) region and a first 3-D channel structure, the S/D region physically contacting the first 3-D channel structure, and an opening (720) extending into the S/D region, a bottom of the opening being below the first 3-D channel structure; and a metallic plug disposed in the opening, the metallic plug being electrically coupled to the S/D region.
Example 17. The device of example 16, where the first 3-D channel structure is a single fin.
Example 18. The device of one of examples 16 or 17, where the first 3-D channel structure includes a first plurality of channel regions, each of the first plurality of channel regions including a nanosheet.
Example 19. The device of one of examples 16 to 18, where the S/D region includes an epitaxially grown semiconductor region.
Example 20. The semiconductor device of one of examples 16 to 19, further including an insulating region disposed below the S/D region, where the S/D region includes an epitaxially grown semiconductor region, and where a bottom of the metal plug is in physical contact with the insulating region.
While this invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative embodiments, as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to the description. It is therefore intended that the appended claims encompass any such modifications or embodiments.
Claims
1. A method of forming a semiconductor device, the method comprising:
- forming, in a substrate, an active region protruding vertically from a major surface of the substrate, the active region comprising a semiconductor source-drain (S/D) region and a first 3-D channel structure, the S/D region physically contacting the first 3-D channel structure, and
- forming an opening extending into the S/D region, the opening having a depth greater than half of a height of the first 3-D channel structure; and
- forming a metallic plug in the opening, the metallic plug making electrical contact with the S/D region.
2. The method of claim 1, wherein forming the active region comprises forming a first sacrificial gate stack over the first 3-D channel structure, wherein forming the metallic plug comprises forming a portion of the metallic plug along a sidewall of the first sacrificial gate stack.
3. The method of claim 1, wherein the active region comprises a second 3-D channel structure, the S/D region physically contacting the second 3-D channel structure.
4. The method of claim 3, further comprising:
- forming a first sacrificial gate stack over the first 3-D channel structure and a second sacrificial gate stack over the second 3-D channel structure, wherein forming the metallic plug comprises forming a portion of the metallic plug along a sidewall of the first sacrificial gate stack and a sidewall of the second sacrificial gate stack.
5. The method of claim 1, wherein forming the active region comprises forming an insulating region over a portion of the major surface of the substrate.
6. The method of claim 5, wherein forming the opening exposes a surface of the insulating region.
7. The method of claim 1, wherein the S/D region is covered by an insulating contact interlayer dielectric (ILD), and wherein forming the opening comprises:
- performing a first etch process to form a first opening in the contact ILD, the first opening exposing a contact etch stop layer covering a surface of the S/D region;
- after completing the first etch process, forming a spacer over sidewalls of the first opening;
- performing a second etch process to remove the exposed contact etch stop layer; and
- performing a third etch process to extend the first opening into the S/D region.
8. The method of claim 7,
- wherein the spacer comprises silicon oxide, or silicon nitride.
9. The method of claim 7, further comprising: after completing the third etch process, selectively removing the spacer formed in the first opening.
10. The method of claim 1, further comprising:
- siliciding a portion of the S/D region exposed by the opening.
11. The method of claim 10, wherein the siliciding forms a metal silicide comprising titanium silicide, cobalt silicide, nickel silicide, platinum silicide, or ruthenium silicide.
12. A method of forming a semiconductor device, the method comprising:
- forming a plurality of nanosheets comprising a first nanosheet and a second nanosheet, each of the plurality of nanosheets having a horizontal central plane and spaced apart from one another in a vertical direction;
- forming a source-drain (S/D) region at a distal end of each of the plurality of nanosheets;
- from a major surface of the S/D region, forming an opening extending through the horizontal central planes of the first and the second nanosheets into the S/D region; and
- filling the opening with a metal to make electrical contact with the first and the second nanosheets through the S/D region.
13. The method of claim 12, wherein filling the opening with a metal comprises filling with tungsten, copper, cobalt, ruthenium, titanium, tantalum, titanium nitride, tantalum nitride, or a combination thereof.
14. The method of claim 12, wherein filling the opening with a metal comprises forming a conductive liner along sides and a bottom of the opening prior to filling the opening with the metal.
15. The method of claim 14, wherein the conductive liner comprises titanium, titanium silicide, cobalt, cobalt silicide, nickel, nickel silicide, platinum, platinum silicide, ruthenium, ruthenium silicide, titanium nitride, tantalum, tantalum nitride or a combination thereof.
16. A semiconductor device comprising:
- an active region protruding vertically from a major surface of a substrate, the active region comprising a semiconductor source-drain (S/D) region and a first 3-D channel structure, the S/D region physically contacting the first 3-D channel structure, and
- an opening extending into the S/D region, a bottom of the opening being below the first 3-D channel structure; and
- a metallic plug disposed in the opening, the metallic plug being electrically coupled to the S/D region.
17. The device of claim 16, wherein the first 3-D channel structure is a single fin.
18. The device of claim i6, wherein the first 3-D channel structure comprises a first plurality of channel regions, each of the first plurality of channel regions comprising a nanosheet.
19. The device of claim 16, wherein the S/D region comprises an epitaxially grown semiconductor region.
20. The semiconductor device of claim 16, further comprising an insulating region disposed below the S/D region, wherein the S/D region comprises an epitaxially grown semiconductor region, and wherein a bottom of the metal plug is in physical contact with the insulating region.
Type: Application
Filed: Oct 5, 2021
Publication Date: Jul 21, 2022
Inventors: Andrew Metz (Albany, NY), Caitlin Philippi (Albany, NY), Sophie Thibaut (Allbany, NY)
Application Number: 17/494,460